[PATCH v3 24/35] x86/bugs: Add attack vector controls for mmio

David Kaplan
2025-01-08T20:25:56Z

Use attack vectors controls to determine if mmio mitigation is required.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
---
arch/x86/kernel/cpu/bugs.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index af5aaa0397c7..4249a1f1524c 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -676,9 +676,12 @@ static void __init mmio_select_mitigation(void)
return;

/* Microcode will be checked in mmio_update_mitigation(). */
- if (mmio_mitigation == MMIO_MITIGATION_AUTO)
- mmio_mitigation = MMIO_MITIGATION_VERW;
-
+ if (mmio_mitigation == MMIO_MITIGATION_AUTO) {
+ if (should_mitigate_vuln(X86_BUG_MMIO_STALE_DATA))
+ mmio_mitigation = MMIO_MITIGATION_VERW;
+ else
+ mmio_mitigation = MMIO_MITIGATION_OFF;
+ }
}

static void __init mmio_update_mitigation(void)
@@ -739,7 +742,8 @@ static void __init mmio_apply_mitigation(void)
if (!(x86_arch_cap_msr & ARCH_CAP_FBSDP_NO))
static_branch_enable(&mds_idle_clear);

- if (mmio_nosmt || cpu_mitigations_auto_nosmt())
+ if (mmio_nosmt || cpu_mitigations_auto_nosmt() ||
+ cpu_mitigate_attack_vector(CPU_MITIGATE_CROSS_THREAD))
cpu_smt_disable(false);
}

--
2.34.1